The name protein is derived from the Greek term proteos, which means “primary” or “to take place first.” Protein was first identified in a laboratory over a century ago at which time scientists described it as a nitrogen-containing part of food that is essential to human life. While protein has long been the darling of the sport, bodybuilding and fitness community, over the past few years there has been more attention focused on the importance of protein during weight loss, advancing age and general health.

What’s the difference between protein and amino acids?

While there are hundreds of different proteins in the human body and thousands in nature, all proteins are based on links of smaller molecules called amino acids. Said another way, amino acids are the “building blocks” of proteins, and only twenty are used to make the proteins in humans and all other life forms. Even ­though the final functional form of proteins may contain minerals or other non-protein components, the basis for these proteins is still amino acids.

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What are “amino acids”?

We now know that all proteins are made up of amino acids (See Amino Acid). All amino acids have the same basic design (see Amino Acid). There is both a nitrogen-containing amino portion and carbox­ylic acid portion attached to a central carbon atom. The presence of both an amino and an acid portion on each molecule led to the name amino acid for this family of molecules. There is also always a hydrogen atom attached to the central carbon, as well as a mysterious “R” group. The R group denotes the portion of an amino acid that will be different from one amino acid to the next. The R portion of an amino acid may be as simple as a hydrogen atom, as in glycine, or much more complex to include carbon chains and rings, acid or base groups, and even sulfur (S). The structure of the twenty amino acids used to make protein is shown in Amino Acids.

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Are there amino acids important to nutrition that are not part of protein?

Not all of the amino acids found in foods and the human body are part of protein or even used to make protein for that matter. Examples of amino acids important in our body but not used to make protein include taurine, citulline, homocysteine and beta alanine. Meanwhile there are several other important “amino” molecules made from amino acids like carnitine, carnosine, sarcosine, creatine and GABA (gamma-aminobutyric acid).